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Appl. Environ. Microbiol., Nov 1997, 4494-4503, Vol 63, No. 11
J Wireman, CA Liebert, T Smith and AO Summers
Gram-negative fecal bacterial from three longitudinal Hg exposure
experiments and from two independent survey collections were examined for
their carriage of the mercury resistance (mer) locus. The occurrence of
antibiotic resistance was also assessed in both mercury- resistant (Hgr)
and mercury-susceptible (Hgs) isolates from the same collections. The
longitudinal studies involved exposure of the intestinal flora to Hg
released from amalgam "silver" dental restorations in six monkeys. Hgr
strains were recovered before the installation of amalgams, and frequently
these became the dominant strains while amalgams were installed. Such
persistent Hgr strains always carried the same mer locus throughout the
experiments. In both the longitudinal and survey collections, certain mer
loci were preferentially associated with one genus, whereas other mer loci
were recovered from many genera. In general, strains with any mer locus
were more likely to be multiresistant than were strains without mer loci;
this clustering tendency was also seen for antibiotic resistance genes.
However, the association of antibiotic multiresistance with mer loci was
not random; regardless of source, certain mer loci occurred in highly
multiresistant strains (with as many as seven antibiotic resistances),
whereas other mer loci were found in strains without any antibiotic
resistance. The majority of highly multiresistant Hgr strains also carried
genes characteristic of an integron, a novel genetic element which enables
the formation of tandem arrays of antibiotic resistance genes. Hgr strains
lacking antibiotic resistance showed no evidence of integron components.
Copyright © 1997, American Society for Microbiology
Association of mercury resistance with antibiotic resistance in the gram-negative fecal bacteria of primates
Department of Microbiology, University of Georgia, Athens 30602-2605, USA.
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